Structure and biomineralization of calcium silicate glasses containing fluoride ions

The in vitro bioactivity, in terms of apatite-forming ability, of calcium silicate glasses containing 10 mol% fluoride ions in the NaF-CaO-SiO₂ system was examined by soaking in Kokubo's simulated body fluid (SBF) at 36.5°C for 7 d. The surface structure of the glasses was examined by thin-film X-ray diffraction (TF-XRD) and Fourier transform infrared reflection spectroscopy (FT-IR) in order to confirm the apatite deposition. The structure of the calcium silicate glasses was examined by ²⁹Si magic angle spinning-nuclear resonance spectroscopy (MAS-NMR) and X-ray photoelectron spectroscopy (XPS). Three calcium silicate glasses containing 10 mol% fluoride ions had different apatite-forming abilities. In the case of CaO/SiO₂=1, the apatite-forming ability of 10NaF·45CaO·45SiO₂ was lower than that of 50CaO·50SiO₂. This indicated that the addition of fluoride ions suppressed the apatite-forming ability, irrespective of the structural similarity of the silicate network based on the ratio of CaO/SiO₂ between the glasses.